The present invention relates to an improved connection for the blanking plug or bonnet to be used in being secured to a choke body so that they will not be a hazard while being removed from the choke body or when they have been subjected to corrosive fluids.
Prior to the present invention chokes designed for use with corrosive fluids such as hydrogen sulphide have had threaded connections for connecting the blanking plug and the bonnet to the choke body. As these threads are subjected to the corrosive action of the fluids passing through the choke, the corrosive fluids have been found to attack the threaded connections between the body and each of the blanking plug and the bonnet.
Additionally, chokes have had a blanking plug connected into the choke body by the use of a securing ring or nut and have included a tapered sealing shoulder for engaging the tapered seat within the choke body. This structure is illustrated in the drawings and described in the specification. The disadvantage of such structure is that if the securing ring or nut is unthreaded while there is pressure in the choke body, the blanking plug will be forcibly ejected from within the choke body.
The U.S. Pat. No. 4,133,560 discloses a plug for connecting into a pressure container and the plug includes an outer flange and inner opposed projections which pass through recesses in the hole in the pressure container so that when the plug is rotated the projections and the flange engage opposite sides of the wall of the pressure contained. This structure is designed to protect the plug from releasing from the wall if the weld securing the plug to the container fails.
U.S.Pat. No. 3,574,359 discloses a conduit coupling including a socket and a plug with the plug being fully inserted into the socket and detents in the socket held in place by a sleeve threaded to the exterior of the socket to retain the plug in its desired connected position.
U.S.Pat. No. 4,249,670 a cap for connection to a pressure tank and having a pressure venting means which allows tank pressure to be vented prior to unlocking and removing the cap. The cap assembly includes an internal tubular member threaded onto a tube connecting to the pressure tank and a cap surrounding the tubular member and having a J slot and pin type of connection therebetween. The cap is biased in a direction to maintain its connection to the tubular member and at a position in which there is a seal between the exterior of the tubular member and the interior of the cap. The cap includes an inner groove which when opposite the seal allows venting of the pressure from the interior of the tubular member.
Some companies have in the past provided fittings and joints which involve the inclusion of a plug held within the passage with a gland nut and a vent port which allows the venting of any fluid under pressure to which the plug is exposed prior to the completion of the unthreading of the gland nut.